Force reversing buffer mechanisms



y 2 1956 K. J. J. MCGOWAN 2,747,860

FORCE REVERSING BUFFER MECHANISMS Filed Sept. ISO, 1950 4 Sheets-Sheet 1 IN V EN TOR.

May 29, 1956 K. J. J. MOGOWAN FORCE REVERSING BUFFER MECHANISMS 4 Sheets-Sheet 2 Filed Sept. 30, 1950 INVENTOR. 6% J 601062.

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M932 MSW W May 29, 1956 K. J. J. MOGOWAN FORCE REVERSING BUFFER MECHANISMS 4 Sheets-Sheet 4 Filed Sept. 30, 1950 Q x k N I INVENTOR. e66 J .M6oar/a12. BY

sWN I United States Patent 2,747,860 FORCE REVERSING. BUFFER MECHANISMS Kenneth J. J. McGowan, Pittsburgh, Pa., assignor to Westinghouse Air Brake Company, a corporation of Pennsylvania Application September 30, 1950, Serial No. 187,789

' 13 Claims. (Cl. 267-4) My invention relates tobuffer mechanisms, and particularly to a force reversing buffer mechanism for use in connection with railway spring switches which are at times trailed.

Spring switch installations on railroads provide means for making trailing traffic moves from a siding onto the main line, or from one track to another track depending onv the direction of the move without the need or requirement of stopping the train or car and throwing the switch to a reverse position. beforecompleting the move. Such installations also permit the move to be made without stopping the train or car after the move has been made to reset the switch. The spring switches used in such installations are provided with springs which. resiliently connect the movable rails to the respective switch operating mechanisms. The resilient connection of the switch points permits the switch to be trailed, the spring bias returning the points to their normal. or closed position.

In trailing a spring switch, the flanges of: the car wheels move the switch points toward their reverse or open positions, thereby increasing the biasing force exerted by the spring connection. As soon as the car'wheels roll off the points, the spring will snap the points: toward their normal or closed position, the points being operated against the flanges of the next set of car wheels. The continuous slapping of the switch points by and against the car wheels results in undesirable wear on the switch points, and the resultant vibration may cause damage to the switch operating stand.

To minimize the wear in spring switch installations due to the slapping of the switch points, bulfer mechanisms and other devices have been provided" for such installations which hold the switch points in their reverse or open position after being trailed for a predetermined period of time and/or retard the return: of the switch points by the spring to the normal or closed positions. While such bufier mechanisms and devices have reduced the slapping of the switch points to great extent, such mechanisms required the switch points to be moved by the flanges of the car wheels toward their open or re verse positions. The moving. of the points by the car wheels during a trailing move may cause some damage to the points which would be detrimental in permitting high speed facing point moves'over the spring. switch.

It is an object of my invention to provide a bufler mechanism for a spring switch wherein the movement of the switch points a predetermined distance away from their normal positions during a trailing move will. cause a reversed force to be applied to the switch points by the buffer mechanism. to bias the switch points the remainder of the distance to their open or reversed positions.

A further object of this invention is to provide a force reversing buffer mechanism for a spring. switch which will retard the return of the switch points: from their trailed positions to their normal. or closed. positions.

Another object of my invention is to provide a force reversing buifer mechanism for a spring switch whereby Patented May 29, 1956 a reversed force is applied to the switch points to move the switch. points additional increments of the distance the switch points are moved during a trailing move.

Still another object of my invention is to provide a double actin'g, force reversing buffer mechanism for a spring switchv which. will: operate ina forward direction as well as in a reverse direction should the switch be trailed in either its normal or reverse position.

A further object of the invention is to provide a force reversing bulfer mechanism. for a spring switch wherein the energy stored in: the buffer spring of the mechanism resulting from. a trailing move is contained by the mechanism should the switch be reversed by the operation of the hand-throw lever of the operating stand.

In carrying out my invention I provide a double-ended cylinder arrangement mounted on the head rod of a spring switch, in which two independent piston assemblies are slidably received, the two piston assemblies being biased to their extreme outer positions against the cylinder heads by a buifer spring. The two piston assemblies are similar, both being of cylindrical form, the end of one assembly being slidably received in a fiuidtight arrangement within the other, and both acting in turn as cylinders for two small pistons receivable therein and fixed in spaced relation on a piston rod. The two piston assemblies are each provided with a by-pass valve, while each of thetwo small pistons cooperate with a dual valve arrangement. The piston rod is provided with two spaced relieved portions forming cavities within the space which cooperate with the dual valve arrangements.

The buffer mechanism is filled with a suitable fluid, such as light oil. The buffer spring is initially stressed when the switch points and switch operating mechanism are in their normal positions by taking up on a coupling interconnecting; the piston rod and the switch operating rod.- The take-up on the coupling will cause a relative movement with respect to the cylinder arrangement of the small. pistons and one of the piston assemblies. One piston assembly is thus spaced from its cylinder head to form a pressure cavity within the piston assembly. The positioning of the one piston assembly will also close the first valve and open the second valve of the cooperating dual valve arrangement. The dual valve arrangement provided for the other piston assembly will have its two' valves in opposite positions, i. e., the first valve open and the second valve closed, the open valve venting the interior of the second piston assembly behind the closed first valve.

When the spring switch is trailed, merit. described will be moved relative to the piston rod, thereby moving one piston assembly relative to theother to-te'lescope the two piston assemblies. The hydraulic pressure in front of one piston will increase due to the decrease in volume of. the fluid cavity formed in and by the piston rod within the piston assemblies. The increased pressure of the fluid in the cavity will cause the stationary piston assembly to move in a direction opposite to the movement of the cylinder arrangement. The cylinder arrangement will be moved relative to the piston rod a predetermined distance by the trailed switch, the increasing fluid pressure continuing. to move the one piston assembly toward the other piston assembly moved by the moving cylinder arrangement.

The high pressure of the cavity in the piston rod is finally relieved when the closed second valve of the second d'ual valve arrangement is brought in alignment with the cavity in the piston rod. This valve now opens relieving. the pressure which would permit the piston assemblies to return to their initial positions under the influence of the stressed buffer spring. The tendency of the cylinder arrangeis checked by the closing of the'by-pass valves associated with the assemblies. Consequently the fluid behind the piston assemblies is under pressure. This pressure is transmitted to the cylinder head to move the cylinder arrangement in the direction in which it was moved by the trailed switch, thereby moving the switch points of the spring switch to their full reverse or open position.

A small leak orifice is provided in each of the piston assemblies to permit the return of the piston assemblies to their initial positions to restore the switch points to their normal positions.

The same action, although in obverse order, takes place when the switch is trailed in its reverse position. In this instance the second piston assembly and the second small piston control the action of the valves.

In a second embodiment of my invention I provide a similar buffer mechanism in which the cylinder arrange ment is moved by the hydraulic pressure due to the compressed buifer spring additional increments of the distance the cylinder arrangement is moved by the trailed switch. The valve arrangements provided in my second embodiment are in many respects similar to the valve arrangements of the first embodiment.

Other objects and characteristic features of my inven tion will become apparent as the description proceeds.

i shall describe two forms of buffer mechanisms embodying my invention, and shall then point out the novel features thereof in claims.

In the accompanying drawings, Fig. l is a plan view of a railway switch operated by a switch operating mechanism and showing the connection of my bufier mechanism to the head rod of the switch and the operating rod of the switch operating mechanism. Fig. 2 is a view of the buffer mechanism and switch operating parts taken along the section line lI-II of Fig. 1. Fig. 3 is a vertical longitudinal view of my bulfer mechanism. Figs. 4 and 5 are fragmentary enlarged sectional views of the valve assemblies shown in Fig. 3. Fig. 6 is an enlarged sectional view taken along the line Vl--VI of Fig. 3. Fig. 7 is a sectional view taken along the line VII-VII of Fig. 4. Fig. 8 is a longitudinal view similar to Fig. 3 of a second embodiment of my invention. Fig. 9 is an end elevational view of the buifer mechanism illustrated in Fig. 8. Fig. 10 is a fragmentary enlarged sectional view of the dual valve assembly shown in Fig. 8. Fig. 11 is a sectional view taken along the line XI-XI of Fig. 10, while Fig. 12 is an elevational view of the circular relief valve 101 hereinafter described.

Similar reference characters refer to similar parts in each of the several views.

Referring to Figs. 1 and 2 of the drawings, the refcrence character A designates a railway switch comprising two fixed rails 1 and 1a and two movable rails 2 and 2a. The fixed rails are laid on the tie plates 3 and are secured to the crossties 4 in the usual manner. The movable rails 2 and 2a are fastened together by a front rod 5 and a head rod 6, and may be moved into a normal position or reverse position by means of a switch operating mechanism B which is connected with the head rod 6. When the switch A is in its normal position as illustrated in Fig. 1, the movable rail 2 engages the fixed rail 1 and the movable rail 2a is spaced away from the fixed rail 1a. When the switch is reversed, the movable rail 2a engages the fixed rail 1a while the movable rail 2 is spaced from the fixed rail 1.

The switch operating mechanism B is similar to the switch operating mechanism described in Letters Patent of the United Sttaes No. 2,387,826 granted to Herbert L. Bone on October 30, 1945, for Railway Switch Operating Mechanisms. The switch operating mechanism is bolted in the usual manner to the crossties 4 and is provided with a hand-throw lever 7 cooperating through suitable mechanism (not shown) with a operating crank 7a supported from a housing 8 provided for the mechanism. The operating crank 7a is pivoted to a jaw 9 by way of a pin 9a, the jaw being fixed to a switch operating rod 10. The operating rod has threaded thereon two spaced stops 11 and 12 locked in place by nuts 11a and 12a. The stop 11 affords a positive stop in conjunction with the casing 8 for undesired motion of the operating rod when the buffer spring forces are reversed during a trailing movement when the switch is in its normal position, the stop 12 serving the same function when the switch is trailed in its reverse position, as will hereinafter be described.

The end of the switch operating rod is fastened by way of a threaded coupling 13 and locknut 13a to the end of a piston rod 14 of my novel buffer mechanism 15. The buffer mechanism 15 is pivotally supported on two spaced lugs 16 on the head rod 6 by way of two vertical trunnions 17 formed on a central housing 18 ot the butter mechanism, the trunnions being received within suitable openings in the spaced lugs.

It will be appreciated from the foregoing brief description of the switch A and the switch operating mechanism B, that rotation of the hand-throw lever 7 approximately degrees in a counterclockwise direction when viewed from the right side in Fig. 1, will move the switch to its reverse position by way of crank 7a, jaw 9, the switch operating rod 10, buffer mechanism 15, and the head rod 6 so that the movable rail 2a will be against the fixed rail 1a. Clockwise rotation of the hand-throw lever 7 will move the switch back to its normal position in which the movable rail 2 will be against the fixed rail 1 as illustrated in Fig. 1.

Referring now in detail to Figs. 3 to 7, the butter mechanism 15 comprises the central housing 18 and two end cylinders 19 and 19a screwed into threaded openings 18a provided in the ends of the housing. The cylinder 19 is closed at its outer end by a cylinder head 20, while the open end of cylinder 19a is closed by a cylinder head 21 provided with a conventional packing gland 22 and nut 23 to accommodate the piston rod 14.

Assembled within the cylinders 19 and 19a are two piston assemblies 24 and 24a, respectively, biased to their extreme outer positions against their cylinder heads by a coil spring 25. For reasons hereinafter appearing, the piston assembly 24 is illustrated in Fig. 3 in spaced relation with respect to the cylinder head 20. The two piston assemblies are of similar construction, and a dc scription of one assembly will therefore be sufficicnt for a complete understanding of the construction of the other assembly, the same reference characters being applied to the same parts followed by the distinguishing subscript a for the right-hand assembly.

The piston assembly 24 comprises a cylindrical member 26 having threaded thereon a piston member 27 provided with piston rings 28 in the usual manner to minimize fluid leakage. The piston member 27 is formed vxith a plurality of elongated arcuate ports 29 (Fig. 6). The ports 29 terminate in valve seats 30 engaged by a spring biased annular valve member 31, hereinafter referred to as the ring relief valve 31. The ring relief valve 3! is formed with an annular lip 32 (Fig. 5) forming a spring seat for one end of a coil compression spring 33 encircling the cylindrical member 26, the other end of the spring being held by a ring 34 fixed adjacent the end of the cylindrical member. A second ring 35 fixed to the member 26 and spaced from the ring 34 serves as a stop for the ring relief valve 31. For purposes hereinafter appearing, the ring relief valve 31 is formed with a cut-out portion which registers with one of the ports 29 to form a relief orifice 36 (Fig. 5).

Adjacent the inner end of the cylindrical member 26 are a plurality of relief ports 37, while the internal surface of the inner end is provided with threads 38 for supporting a cylindrical member 39 of reduced diameter which extends slightly beyond the middle of the central housing 13. It will be noted that the extending end of the cylindrical member 39 forming a part of the piston assembly 24 is slidably received within the cylindrical greases member 39a forming a part of the piston assembly 24a, piston rings 40 being provided adjacent the ends of member 39a to minimize fluici leakage between the parts of the two assemblies.

Slidably received with the cylindrical members 26 and 26a of the two piston assemblies are small pistons 41 and 41a, respectively, fixed in spaced relation on reduced portions 42:: of a piston rod extension 42. The pistons 41 and 41a are provided with suitable piston rings 43 and 43a. For purposes hereinafter appearing, the piston rod extension 42 is formed with relieved portions 44 and 45 which are so spaced that when the two piston assemblies 24 and 24a are in their extreme positions illustrated in Fig. 3, the two relieved portions are located approximately equidistant on opposite sides of the center line of the buffer mechanism. The piston rod extension reecived within the cylindrical member 39 of the piston assembly 24 forms a space or channel 46 between the rod and the interior of the cylindrical member, the relieved portion 44 forming a cavity 47. The piston rod extension received within the cylindrical member 39a forms a similar space or channel 48, the relieved portion 45 of the rod forming a cavity 49.

An internal annular recess 50 is provided in the cylindrical member 26 adjacent to the inner ends of the threads 38 (Fig. 4). Received within said recess and clamped in place by the cylindrical member 39 is an annular insert 51 having a ring portion 52 extending in back of, but spaced from the ports 37 of the member 26. For purposes hereinafter appearing the insert 51 is further provided at its inner end with a bevelled surface 53 forming a valve seat, and a shoulder 54 forming a spring abutment means.

Adjacent to the right-hand end of the small piston 41 and encircling the piston rod is a circular relief valve 55 having a plurality of ports 56 formed at its inner edge by radial legs or extensions 57 (Fig. 7), and having an extending ring portion 58 at its outer edges. A suitable piston ring 59 is provided for the valve 55. A coil compression spring 60 encircling the piston rod and interposed between the small piston and the circular relief valve 55 biases the valve against the seat formed by the edge of the extending ring portion 52 of the insert 51. It will be noted that the extending ring portions 52 and 58 form a vent to the relief ports 37 which is effectively sealed by the circular relief valve 55.

An annular relief valve 61 is also provided for cooperation with the insert 51 and the circular relief valve 55', the annular valve being slidably receivable in a fluidtight relationship on the piston rod extension 52. The annular valve 61 is provided at its inner end with an extending ring portion 62, the rear surface of which is bevelled as at 63. The outer end of the circular valve is provided with a radially outwardly extending ring 64+ to form a shoulder 65. Interposed between the shoulder 65 of the annular relief valve and the shoulder 54 of the insert 51 is a coil spring 66 tending to bias the annular relief valve in an outward direction against the inner face of the circular relief valve 55. The spring 6%) biasing the circular relief valve 55 against the ring 52 of the insert is made stronger than the spring 66. Thus, if the circular valve 55 is maintained in a closed position to seal off the port 37 in the manner hereinafter described, the annular valve 61 will be maintained in a position wherein the bevelled surface 63 is spaced from the valve seat 53 of the insert. A passage is thus provided from the space 48, cavity 49, cavity 47, and space 46, through the open annular valve 61 to the inner side of the small piston 41.

it will be noted that the valve assemblies on the right side of the buffer mechanism are similar to those described for the left side of the mechanism and have been given the same reference characters followed by the subscript a. In the case of the valve assemblies on the right side, the annular valve 61a is illustrated in Fig. 3 as being closed, while the circular valve 55a is shown open to provide a passageway to the relief ports 37a.

In placing the buffer mechanism 15 into operation, all available interior space Within central housing 18, the end cylinders 19 and 19a, including the channels 46 and 48 and the cavities 47 and 49, is filled with a suitable operating fluid such as a light oil. For this purpose a filler plug 67 is provided on the central housing 18; drain plugs 68 being provided on both sides of the housing near the bottom wall for emptying the buffer mechanism.

With the switch A and the switch operating mechanism B both in their normal positions as illustrated in Fig. I, the buffer spring 25 is initially stressed to apply an initial biasing force to the switch points to hold them in their normal positions with a predetermined force. The coupling 13 interconnecting the end of the piston rod 14 and the operating rod It? is turned by a wrench or other suitable tool while the piston rod 14 is held against turning. Referring to Figs. 3 and 4, it will be noted that the cylindrical members 26 and 2611 are provided on their inner surfaces with integral annular shoulders 69 and 69a, respectively. The movement of the piston rod 14 to the right caused by taking up on the coupling 13 brings the inner end of the small piston 41 into engagement with the shoulder 69. The cylindrical member 26 is thus moved to the right, away from the cylinder head 20 to form. a cavity 70. The buffer spring 25 is compressed due to abutment of the cylindrical member 26a against the cylinder head 21. The piston assembly 24 may be readily moved in making this adjustment in view of relieved sections 71 (Figs. 3, 5, and 6) provided in the cylindrical member 26 and straddling the piston member 27. The initial stressing of the spring 25 serves to provide a biasing force for maintaining the movable rail 2 against the fixed rail 1 under pressure when the switch is in its normal position as illustrated. When the parts are adjusted in the manner illustrated and described, the coupling 13 is made secure by the locltnut 13a.

The parts are so proportioned and the throw of the rank inso adjusted that when the switch operating mechanism is operated to its reverse position, the piston rod 14 will be inserted into the buffer mechanism so that the small piston 41a moves to the left carrying the piston assembly 24a therewith, the buffer spring 25 forcing the piston assembly 24 against the cylinder head 2i) so that the entire buffer mechanism is moved to the left to reverse the switch points, the biasing force of the buffer spring maintaining the movable rail 2a against the fixed rail in.

The movement of the small piston 4-1 to the right in initially stressing the buffer spring 25 when the switch A is in its normal position, tends to increase the bias of the spring 60, thereby holding the circular valve 55 againstthe valve seat formed by the extending ring 58 of the annular insert 51. The inner side of the circular valve 55 being abutted by the outer end of the annular valve 61 will hold the valve 61 open as illustrated in Figs. 3 and 4. As previously described the biasing spring 6% for the circular valve 55 is stronger than the biasing spring 66 provided for the annular valve 61, so that the biasing spring 69 will overcome the biasing spring 66. it will be noted that the circular valve 55a is open and the annular valve 63:: is closed on the right side of the buffer mechanism 15. The movement of the piston rod to the right in initially stressing the spring 25, moves the small piston 41:; to the right, thereby relieving the biasing spring 66a of the circular valve. The biasing spring 66a for the annular valve 61a thus closes the annular valve and in so doing moves the circular valve to the right against the stop provided by the inner side of the annular shoulder 60a, to hold the annular valve open.

When the switch A is trailed in its normal position, the wheels of the passing car or train will tend to move the movable rail 2 away from the fixed rail 1 and the movable rail 2a toward the fixed rail in. The movement of the movable rails will move the head rod 6 to the left with respect to the switch operating rod 10. The housing 18 and the cylinders 19 and 19a will be moved to the left by the head rod 6 relative to the piston rod 14 which is coupled to and held by the switch operating rod 10.

For a clearer understanding of the operation of the buffer mechanism, the description of operation hereinafter given will assume the housing 18 and the cylinders 19 and En as remaining stationary and the piston rod 14 as moving and being moved to the right.

The relative withdrawal of the piston rod to the right will move the piston assembly 24 therewith to the right. The movement of the piston assembly will cause a displacement of the fluid in the cavity 4? due to the telescoping of the piston assemblies 24 and 24a. Since the annular valve 61 is open and the annular valve 61a is closed, the fluid in channels 46, 48 and in cavities 47, 49 will enter the cavity between the small piston 41 and the circular valve 55 sealing the ports 37. The fluid in the channels and cavities will be under pressure due to the decreasing volume of the cavity 49 due to the movement of the piston rod and piston assembly 24. The fluid under pressure entering the cavity in back of the circular valve will force the piston assembly 24 ahead of the small piston 41. It will be appreciated that the movement of the piston assembly to the right will not be retarded due to any building up of pressure ahead of the piston member 27. The relieved portions '71 of the cylinder 19 and the open ring valve 31 will permit the free flow of fluid through and around the piston member 27. The continued withdrawal of the piston rod 14 will move the small piston 41 to the right while the piston assembly 2 will be moved to the right an equal distance plus increments of the distance the piston 24 is moved due to the increases in the hydraulic pressure.

it will be understood that the withdrawal of the piston rod 14 moves both of the small pistons 41 and 41a. The movement of the small piston 41a will not be retarded by any hydraulic pressure building up behind it during its movement. The fluid within the cylindrical member 26a behind the small piston will flow out the end of the cylindrical member, past the cylinder head 21 and around the piston member 2711 by way of the leak grooves 71a formed in the cylinder i911.

At a point where the relieved portion 45 of the piston rod extension 42 is aligned with the left-hand end of the closed annular valve Girl, the piston assembly 24 has been moved to the right a greater distance than the small piston 4.1. The buffer spring will thus be under compression tending to move the piston assembly 24 to the left, the piston assembly however being held in its forward position by the fluid pressure in the channels 45, 48 in the cavities 47, 45 and in the cavity between the small piston 43. and the circular valve 55. The continued withdrawal of the piston rod 14 will bring the cavity 49 into alignment with the closed annular valve 61a. The alignment of the relieved portion 45 with the right-hand end of valve 610 provides a by-pass to relieve the high pressure of the cavity 3? through the relief ports 37a of the cylindrical member 261:.

The buffer spring 25 being under tension will tend to move the piston assembly 24 to its initial position now that the hydraulic pressure has been relieved. However, any movement of the piston assembly 24 to the left will close the ring valve 31 of the piston assembly. The force of the buffer spring 25 is thus resisted by the fluid in the cavity 76'. The resultant hydraulic pressure on the fluid in cavity '79 will be exerted on the left face of the small piston ll to push the piston rod 14 farther in the direction in which i was withdrawn. The hydraulic pressure which moved the piston rod 14 will be maintained by the closed ring valve 31 thus holding the piston rod 14 in its withdrawn position.

As previously described, the ring valve 31 is provided with a relief orifice 36 which registers with one of the ports 29 provided in the piston member 27. The fluid behind the piston member 27 is thus permitted to leak slowly past the piston member. The reversed force on the small piston 41 will be maintained until sutficient leakage through orifice 36 has taken place which Will permit the piston assembly to return toward its normal position under the urging of the spring 25. When the shoulder 69 of the cylindrical member 26 abuts the inner face of the small piston 41 fixed on the piston rod, the cylindrical member of the piston assembly 24 and the piston rod will move together as a unit toward their normal positions illustrated in Fig. 3. This slow return will continue until the piston member 27 is straddled by the leak grooves 71 formed in the cylinder 19. The return of the piston assembly 24 and the piston to its normal position from this point on will be rapid since no retarding pressure is being applied to the piston member 27. This rapid return will be accomplished by the full force of the buffer spring 25 to drive the piston rod to its normal position.

Applying now the operation of the buffer mechanism as described to the switch A of Fig. 1, it will be readily understood that the movement of the buffer mechanism 15 to the left relative to the piston rod 14 by the trailed switch will telescope the two piston assemblies 24 and 24a to increase the fluid pressure within the assemblies. The release of the fluid pressure will tend to release the compressed buffer spring 25 to return the piston assembly 24 to its normal position. The resulting closure of the ring relief valve 31 will prevent the return of the piston assembly 24, the force of the compressed spring increasing the pressure of the cavity 79. The increased pressure of cavity 70 will act against the cylinder head 20, the piston rod being stationary, to move the butler mechanism 15 an additional distance to the left, thereby moving the switch points to their full reverse positions.

The fluid pressure in cavity 70 acts against the outer surface of piston M as well as against the cylinder head 29. To prevent any movement of the piston rod and to prevent any force from being applied to the crank 7a or other mechanism of the switch operating mechanism B during the force reversing stroke of the butter mechanism, the stop 11 is so adjusted on the operating rod 10 that the inner face of the stop abuts the housing 8 when the switch A and the switch operating mechanism are in their extreme normal positions. The piston rod 14 is thus held stationary, the full force of the fluid pressure in cavity 76) acting against the cylinder head 20 to move the switch points over to their full reverse position when the switch points are moved a predetermined distance by the wheels of a trailing vehicle.

The relief orifice 36 provided in the ring valve 31 permits the slow return to the right of the buffer mechanism l5. When the leak groove '71 formed in cylinder 19 straddles the piston member 27 of the piston assembly 24, the return of the buflier mechanism will be very rapid, the return being accomplished by the full force of the buffer spring to return the movable rails 2 and 2a to their full normal positions as illustrated.

From the foregoing description of my butler mechanism and its operation, it will be readily appreciated that the operation of the device in and from a reverse position of the switch A is identical except in reverse order. In the case of the switch A being in its reverse position and trailed, the housing 18 and the piston assemblies 19 and 19a will be moved to the right relative to the piston rod 14. As previously described, when switch A is in its reverse position, the circular valve 55a is closed and the annular valve 61a is open. Movement of the housing and cylinders to the right will telescope the piston assemblies to increase the hydraulic pressure in cavity 47, the opening of the annular valve 61 relieving the pressure to permit the hydraulic pressure built up in cavity 7% by the buffer spring to move the housing and cylinders farther to the right to move the switch points to their full normal position. Relieving of the hydraulic pressure in cavity 76a through the orifice 36a will eventually permit the return of the housing and cylinders to their extreme reverse positions.

It will be appreciated from the foregoing description that the energy stored in the buffer spring 25 resulting from a trailing move will be contained by the buffer mechanism described. The outward bias of the compressed buifer spring tends to move the piston assemblies 24 and 24a toward their respective cylinder heads. This outward motion however closes the ring relief valves 31 and 31a to prevent the sudden release of the compressed spring. Thus a reversal of the switch points by operation of the hand-throw lever while the spring 25 is still under compression due to a trailing move will not release the compressed spring.

Referring now to Figs. 8 to 12 of the drawings wherein a second embodiment of my invention is illustrated, the buffer mechanism 72 comprises a central housing 73 providedwith rearwardly extending spaced lugs 74, and a filler plug 75 for filling the interior of the buffer mechanism with fluid such as a light oil. The buffer mechanism is fixed to the head rod 6 of the switch A by bolts 76 passing through suitable openings in said lugs and head rod, and nuts 77. Bolted to the ends of the central housing 73 by bolts 78 are end cylinders 79 and 80 closed at their open ends by cylinder heads 81 and 82, respectively, welded tothe cylinders as indicated by the fillers 81a and 82a, respectively. The cylinder head 82 is provided with the usual packing gland 83 to accommodate the piston rod 14.

Slidably received within the end cylinder 79 is a piston assembly 84 similar in most respects to the piston assembly 24 hereinabove described. Similar parts of the piston assembly 34 have been designated by the same reference characters as the parts of the piston assembly 2-4. The piston assembly 84 differs from the assembly 24 by the provision of an annular ring 85 (Fig. within the cylindrical face forming the stop 86 and formed with a relief orifice 87 terminating in a valve seat 88 within the cylindrical member. Threaded to the inner end of the cylindrical member 26 is a cylindrical member 89 of reduced diameter formed on its exterior surface with an annular shoulder 90 and with relief portions 91 in its interior surface. The inwardly extending end of the cylindrical member 39 slidably receives the inwardly extending end of a second piston assembly 92. The piston assembly 92 comprises a tubular member 93, the inwardly extending end of which is provided with piston rings 94, while the outer end is formed with a shoulder 95. Fixed to the tubular member 93 in a suitable manner is a cylindrical member 96 having keyed thereto as at 97 a piston member 98 slidably received within the cylinder 80. The piston member 98 is similar to the piston member 24a and is provided with the piston rings 28a and formed with the relief ports 29a adapted to be closed by the ring relief valve 31a, the ring relief being provided with the leak orifice 36a. biased to their extreme outer positions against the cylinder heads by the buffer spring 25, while the tubular member 93 and the cylindrical member 89 are biased to their outer positions by a spring 250 interposed between the shoulders 95 and 90 of the respective members.

Slidably received within the cylindrical member 96 is the piston rod 14 having a reduced extension 99 slidably receivable within the cylindrical member 96, the tubular member 93 and the cylindrical member 89. Integral with the end of the piston rod extension within the member 96 is an abutment member 100. Fixed to the other end of the piston rod extension is the small piston 41 provided with the piston rings 43.

Cooperating with the piston 41 and the relief orifice 87 is a dual valve arrangement comprising a circular relief valve 101 and an annular relief valve 102 (Figs.

member 26 having a bevelled sur-- i The piston assemblies 84 and 92 are 8 and 10). The circular relief valve cooperates with the valve seat 83 of the relief orifice 87 and is provided with inwardly extending lugs 10$, hereinafter referred to as stops 103 (Figs. 10 and 12). The outer end of the annular relief valve 102 is received within the opening 104 of the valve 101, and is formed with a radially extending portion 105,the inner side of which cooperates with the outer side of the circular relief valve. It will be appreciated that the abutment of the two valves 101 and 102 will form a cavity 106 between the small piston 41 and the dual valve arrangement, and a cavity 107 between the piston rod extension and the cylindrical member 89. In the description hereinafter given of the dual valve operation, it will be understood that when valve 102 is referred to as being closed, the valve 102 abuts the valve 101 to close the passage between the cavities 106 and 107. Similarly, when valve 101 is referred to as being closed it will be understood that valve 161 seals the relief orifices 87.

The inner end of the relief valve 102 is provided with a radially extending ring portion 108, hereinafter referred to as the stop 108. A second radially extending ring portion 109 spaced from the stop 108 is provided for the annular relief valve, and will be hereinafter referred to as the stop 109. The stops 108 and 109 are spaced from an intervening collar 110 (Figs. 10 and 11) fixed within the end of the cylindrical member 89 and formed with radially inwardly extending legs 111 adapted to be engaged by the stops 108 and 109. A spring 112 interposed between collar 110 and the circular relief valve 101 biases this valve to its closed position, while a spring 113 interposed between the circular relief valve 101 and the stop 109 biases the annular relief valve 102 to its closed position.

For purposes hereinafter appearing, it will be noted that with the circular relief valve 101 and the annular relief valve 1152 closed as illustrated in Figs. 8 and 10, the intervening distance between the stops 103 of the valve 101 and the collar 110 is greater than the distance between the stop 109 of the valve 162 and the legs 111 of the collar.

As hereinbeforc described,-the buffer spring 25 is initially stressed by taking up on the coupling 13, the small piston 41 being moved to the right so that engagement of the inner side of the piston and the stop 86 will move the piston assembly 84 to the right. With the switch in its normal position as illustrated in Fig. 1, the parts of the buffer mechanism will be in the positions illustrated in Figs. 8 and 10, the circular relief valve 101 and the annular relief valve 102 being closed.

Considering now the buffer mechanism as being stationary and the piston rod 14 as being moved to the right in the manner described, the relative withdrawal of the piston rod 14 will move the small piston 41 to the right carrying the piston assembly $4 to the right. The increase in the hydraulic pressure in the cavity 107 will keep the circular relief valve 101 closed, but causes the annular relief valve 102 to open, the stop 108 abutting the collar legs 111. The fluid under pressure now enters the cavity 106. As the small piston 41 continues to be moved toward the right, the volume of the cavity 107 will continue to decrease, thus increasing the pressure of the fluid in the cavities 106 and 107. The high pressure of the fluid moves the piston assembly 84 to the right ahead of the small piston 41. This action continues during the relative withdrawal of the piston rod 14, the ratio of motion between the piston assembly and the small piston being dependent on the effective relative diameters of the piston 41 and the tubular member 93.

If we assume that the movement of the switch points toward their reverse position is stopped at any given point, the relative withdrawal of the piston rod 14 will also stop. Since the fluid pressure will tend to equalize itself, the fluid pressures'in the cavities 166 and 107 will be equal, thereby permitting the annular relief valve 192 to be closed by the spring 113. The relative movement of the piston rod 14 to the right had moved the piston assembly 84 to the right, thereby compressing the buffer spring 25. The biased buffer spring 25 will tend to move the piston assembly 84 to the left, thereby closing the ring relief valve 31 and increasing the pressure within the cavity 70. The hydraulic pressure of the cavity 70 will move the small piston 41 to the right. The movement of the piston to the right will increase the pressur in the cavity 106, thereby opening the circular relief valve 101 to relieve the high pressure through the relief ports 87. With the cavity 106 open to reservoir pressure, the small. piston 41 is free to be moved by the hydraulic pressure of the cavity 70 created by the biased buffer spring 25. The piston rod 14 will thus be moved an additional distance in the direction of its withdrawal. The relief orifice 36 provided in the ring relief valve 31 will permit the piston assembly, small piston and piston rod to return to their initial positions in the manner heretofore described.

Applying now the operation of the buffer mechanism. 72 as described to the switch A, the trailed switch will move the buffer mechanism to the left to telescope the two piston assembles 84 and 92. The build-up of pressure in the cavity 107 will move the piston assembly 84 to the right to bias the buffer spring. When the movement of the buffer mechanism ceases, the valve 101 will open to permit the piston assembly 84 to be moved to the left by the compressed spring 25. This tendency to move to the left will be checked by the closed ring valve 31, the pressure in cavity 70 acting on the cylinder head 81 to move the buffer mechanism an additional distance in the direction the buffer mechanism was moved relative to the piston rod by the trailed switch.

The return of the buffer to its normal position is in the same manner heretofore described in connection with the first embodiment of my invention.

The buffer mechanism illustrated in Figs. 8 through 12 will act to retard the return of the switch points to their reverse position when the switch A is in its reverse position and trailed.

Assuming now that the switch A is moved to its re verse position, the movement of the switch operating rod 10 will move the piston rod 14 to the left, the abutment member 100 on the piston rod engaging the inner end of the cylindrical member 96 to move the piston assembly 92 to the left, thereby compressing the springs 25 and 25a. The piston assembly 84 will thus be moved against the cylinder head 81 due to the compressed spring 25, the movement of the piston rod and spring bias causing the head rod 6 to move the switch points to their reverse positions.

Should the switch A be trailed in its reversed position, the buffer mechanism will be moved to the right relative to the piston rod 1.4 telescoping the two piston assemblies 84 and 92 to compress the buffer spring 25. The increase in the hydraulic pressure within the cavity 107 will open the annular valve 102, to permit the fluid under pressure to enter cavity 106. Since the volume of cavity 106 is increasing by virtue of the movement toward the left of the cylinder assembly 84, no increase in hydraulic pressure will occur in the two cavities. 1

When the car wheels roll off the switch points, the compressed buffer spring 25 will tend to return the buffer mechanism to its reverse position. The ring relief valve 31a will accordingly close to contain the compressed buffer spring. The buffer spring is slowly released by the leakage of the fluid through the leak orifice provided in the ring relief valve 310, to return the switch points to their reverse positions.

In the return movement of the buffer mechanism after the switch has been trailed in its reverse position, the coaction of the circular relief valve 101 and the annular relief valve 102 may create a vacuum effect in cavity 107. This can best be understood if we again consider the buffer mechanism stationary, and the piston being moved to the right relative to the buffer mechanism. The movement of the small piston to the right will tend to increase the hydraulic pressure within the cavity 106. The high pressure of the cavity will move the two relief valves 101 and 102 as a unit toward the right, the valve 101 opening to permit the flow of fiuid from cavity 106 through the relief orifice 87. The valve 102, however, is closed preventing the fiow of fluid from cavity 106 to cavity 107. Since the volume of the cavity 107 is increasing, a partial vacuum may be created therein.

As previously described the distance between the stop 103 on valve 101 and the collar 110 is greater than the distance between the stop 109 on valve 102 and the collar legs 111. The continued movement to the right of the two valves 1.01 and 102 by the hydraulic pressure of cavity 106 will engage the stop 109 with the legs 111 before the stop 103 engages the collar 110. Valve 102 is accordingly opened to permit passage of the fluid from cavity 106 to cavity 107 to equalize the pressures in the two cavities.

It will be understood that although I have illustrated and described the buffer mechanism as being mounted on the head rod of the switch and the piston rod coupled to the switch operating rod, the buffer mechanism could very easily be fixed by way of trunnions 17 or lugs 74 to the switch operating rod and the piston rod pivoted or fixed to the head rod 6 of the switch. The operation of the buffer mechanisms would be in the manner described with the piston rod moving with respect to the buffer mechanism to throw the switch points to their opposite positions when the switch is trailed.

From the foregoing description of the buffer mechanisms embodying my invention, it will be appreciated that the force reversing feature of the mechanisms in moving the switch points an additional distance in the direction in which they are trailed instead of the usual kick-back action of the switch points by the wheels, will reduce the wear on the switch points, the operating switch mechanism and associated equipment, all of which tend to reduce the maintenance costs of the spring switches so equipped.

Although I have herein shown and described only two force reversing buffer mechanisms embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

l. A buffer mechanism comprising a housing having two end cylinders containing a fluid, a piston assembly reciprocable in each of said cylinders, the ends of said piston assemblies being telescoped in a fluid tight arrangement, valve means for each of said piston assemblies normally biased to a closed position, a leak orifice in each of said valve means, one of said piston assemblies being cylindrical, said cylindrical piston assembly being provided with relief ports for venting the interior of said assembly; a spring interposed between said piston assemblies biasing the same toward the ends of their respective cylinders, a rod receivable within said piston assemblies, a piston fixed to said rod and reciprocable in said cylindrical piston assembly, means for moving each of said piston assemblies in a given direction upon movement of said rod in said given direction, a first relief valve normally biased to a closed position for sealing the relief ports of said cylindrical piston assembly, a second relief valve coacting with said first valve and normally biased closed, said first and second relief valves dividing the space bounded by said rod within the cylindrical piston assembly into a first cavity between the valves and the piston, and a second cavity in back of said valves, said rod being initially moved in a first direction for moving said cylindrical piston assembly in the same direction to bias said spring; the movement of said rod in said first areas-ea 13 direction. moving said. piston and said cylindrical piston assembly to increase the fluid pressure within said second cavity to open said secor .l relief valve thereby interconnecting said first and second cavities, the increased pressure in front of said piston moving the cylindrical piston assembly ahead of the piston to further bias said spring; the second valve closing when motion of the rod ceases, the biased sprin tending to return the cylindrical piston assembly to its initial position thereby closing the cylindrical piston assembly valve means tending to increase the fluid pressure behind said piston for moving said piston and rod in said first direction thereby increasing the pressure in said first cavity to open said first valve to relieve the pressure through said relief ports, the release of pressure permitting the biased spring to return the cylindrical piston assembly to its normal position, the return of said cylindrical piston assembly increasing the pressure behind said piston to move said piston and rod additional increments of the distance the rod was moved in the first direction; movement of the rod in a second direction moving the other piston assembly in said second direction, the movement of the second piston assembly opening its associated valve means to permit movement thereof to bias said spring, the return movement of said second piston assembly by the biased spring closing its associated valve means; the return movement of both said piston assemblies being retarded by the slow release of the fluid pressure through the leak orifices provided in said piston assembly valve means.

2. A buffer mechanism comprising a housing having two end cylinders containing a fluid, a piston assembly reciprocable in each of said cylinders, valve means for each of said piston assemblies normally biased to a closed position, a leak orifice in each of said valve means, one of said piston assemblies being cylindrical, said cylindrical piston assembly being provided with relief ports for venting the interior of said assembly, a spring interposed between said piston assemblies biasing the same toward the ends of their respective cylinders, a rod receivable within said piston assemblies, a piston fixed to said rod and reciprocable in said cylindrical piston assembly, a first relief valve normally biased to a closed position for sealing the relief ports of said cylindrical piston assembly, a second relief valve coacting with said first valve and normally biased closed, said first and second relief valves dividing the space bounded by said rod within the cylindrical piston assembly into a first cavity between the valves and the piston, and a second cavity in back of said valves, the movement of said rod from its normal position in a first direction moving said piston and said cylindrical piston assembly to increase the fluid pressure Within said second cavity, the increase in pressure opening said second relief valve to interconnect said first and second cavities, the increased pressure in front of said piston moving the cylindrical piston assembly ahead of the piston to bias said spring; the second valve closing when motion of the rod ceases, the biased spring tending to return the cylindrical piston assembly to its initial position whereby the valve means therefor is closed tending to increase the fluid pressure behind said piston for moving said piston in the first direction thereby increasing the pressure in said first cavity to open said first valve to relieve the pressure through said relief ports, the release of pressure permitting the biased spring to return the cylindrical piston assembly to its normal position, the return of said cylindrical piston assembly increasing the pressure behind said piston to move said piston and rod additional increments of the distance the rod was moved in the first direction; movement of the rod from its normal position in a second direction moving the second piston assembly in said second direction and opening its associated valve means to permit movement of said assembly to bias said spring, the return movement of both said piston assemblies by the biased spring closing their associated valve means, the return movement of said piston assemblies being 14 retarded by the slow release of fluid pressure through the leak orifices provided in said piston assembly valve means.

3. A buffer mechanism comprising a housing having two end cylinders containing a fluid, a piston assembly reciprocable in each of said cylinders, valve means for each of said piston assemblies normally biased to a closed position, a leak orifice in each of said valve means, one of said piston assemblies being cylindrical, said cylindrical piston assembly being provided with relief ports for venting the interior of said assembly, a spring interposed between said piston assemblies biasing the same toward the ends of their respective cylinders, a rod receivable within said piston assemblies, a piston fixed to said rod and reciprocable in said cylindrical piston assembly, a first relief valve normally biased to a closed position for sealing the relief ports of said cylindrical piston assembly, and a second relief valve coacting with said first valve normally biased closed; the movement of said rod in a first direction moving said piston and said cylindrical piston assembly to increase the fluid pressure in front of said piston thereby opening said second relief valve, the increased pressure in front of said piston moving the cylindrical piston assembly ahead of the piston to bias said spring; the second valve closing when motion of the rod ceases, the biased spring tending to return the cylindrical piston assembly to its initial position whereby the piston assembly valve means is closed tending to increase the fluid pressure behind said piston for moving said piston and rod in the first direction thereby increasing the pressure in front of said piston to open said first valve, the fluid pressure venting through said relief ports the release of pressure permitting the biased spring to return the cylindrical piston assembly to its: initial position there by increasing the pressure behind said piston to move said piston and rod additional increments of the distance the rod was moved in the first direction; movement of the rod in the second direction moving the second piston assembly in said second direction thereby opening its associated valve means to permit movement of said assembly to bias said spring, the return movement of said second piston assembly by the biased spring closing its associated valve means; the return movement of both said piston assemblies being retarded by the slow release of fluid pressure through the leak orifices provided in said piston assembly valve means.

4. A buffer mechanism comprising a cylinder containing a fluid, a cylindrical piston assembly r'eciprocable in said cylinder, valve means for said piston assembly normally biased to a closed position, a leak orifice in said relief valve, said piston assembly being provided with relief ports for venting the interior of said assembly, a cylindrical member telescoping with said cylindrical piston assembly in a fluid tight arrangement, a spring interposed between said piston assembly and said cylindrical member biasing said assembly toward the end of said cylinder, a rod receivable within said cylindrical member and said piston assembly, a piston fixed to said rod and reciprocable in said piston assembly, a first relief valve normally biased to a closed position for sealing the relief ports venting the interior of said cylindrical piston assembly, a second relief valve coacting with 'said first valve and normally biased closed to bound a cavity within the cylindrical piston assembly between the piston and said valves and a second cavity between the valves and the cylindrical member, means for moving said piston assembly from its normal position upon movement of said piston rod in a first direction, the movement of said rod in said first direction moving said piston and said cylindrical piston assembly to increase the fluid pressure in said second cavity to open said second relief valve to equalize the pressure in both said cavities, the increased pressure in said cavities moving the cylindrical piston assembly ahead of the piston to bias said spring, the second valve closing when motion of the rod ceases,

the biased spring tending to return the cylindrical piston assembly to its initial position thereby closing the piston assembly valve means and tending to increase the pressure within said piston assembly behind said piston for moving the piston in said first direction thereby increasing the pressure in said first cavity to open said first valve to relieve the pressure through said relief ports, the release of pressure permitting the biased spring to return the cylindrical piston assembly to its normal position, the return of said cylindrical piston assembly increasing the pressure behind said piston to move said piston and rod additional increments of the distance the rod was moved in the first direction.

5. A buffer mechanism comprising a housing having two end cylinders containing a fluid, a piston assembly reciprocable in each of said cylinders, valve means for each of said piston assemblies normally biased to a closed position, a leak orifice in each of said valve means, one of said piston assemblies being cylindrical, the end of which slidably receives the end of the other piston assembly in a fluid tight arrangement, said cylindrical piston assembly being provided with relief ports for venting the interior of said assembly, a spring interposed between said piston assemblies biasing the same toward the ends of their respective cylinders, a rod receivable within said piston assemblies, a piston fixed to said rod and reciprocable in said cylindrical piston assembly, abutment means within said cylindrical piston assembly for engagement by said piston upon movement thereof by said rod in a first direction to move said cylindrical piston assembly therewith in said first direction, abutment means on said rod for engaging the second piston assembly upon movement of said rod in a second direction to move said second piston assembly therewith in the second direction, a first relief valve normally biased to a closed position for sealing the relief ports of said cylindrical piston assembly, a second relief valve coacting with said first valve and normally biased closed, said first and second relief valves dividing the space bounded by said rod within the cylindrical piston assembly into a first cavity between the valves and the piston, and a second cavity in back of said valves, a stop member on said cylindrical piston assembly, stop means on said first and second valves adapted to engage said stop member, the distance between the stop member and the stop means of said first valve being greater than the distance between said stop member and the stop means of the second valve, said rod being initially moved in said first direction moving said cylindrical piston assembly in the same direction by the engagement of said piston with the abutment means of said assembly to bias said spring; the movement of said rod from its normal position in said first direction moving said piston and said cylindrical piston assembly to increase the fluid pressure within said second cavity, the increase in pressure opening said second relief valve to interconnect said first and second cavities, the increased pressure in front of said piston moving the cylindrical piston assembly ahead of the piston to bias said spring; the second valve closing when motion of the rod ceases, the biased spring tending to return the cylindrical piston assembly to its initial position whereby the piston assembly valve means is closed to increase the fluid pressure behind said piston to move said piston and rod in said first direction, thereby increasing the pressure in said first cavity to open said first valve to relieve the pressure through said relief ports, the release of pressure permitting the biased spring to return the cylindrical piston assembly to its normal position, the return of said cylindrical piston assembly increasing the pressure behind said piston to move said piston and rod additional increments of the distance the rod was moved in the first direction; movement of the rod in the second direction from its normal position moving the second piston assembly in said second direction by the engagement of the abutment means on said rod and said piston assembly, the movement of the second piston assembly opening its associated valve means to permit movement of said assembly to bias said spring, the return movement of said second piston assembly by the biased spring closing the associated valve means, the return movement of both of said piston assemblies being retarded by the slow release of fluid pressure through the leak orifices provided in each of said piston assembly valve means, said stop member and said stop means on said first and second relief valves cooperating to hold said second valve open to interconnect said first and second cavities during the return movement of the second piston assembly.

6. A buffer mechanism comprising, a housing containing a fluid, a hollow piston assembly reciprocable in said housing, means including a spring biasing said piston assembly in a first direction, a piston reciprocable in said hollow piston assembly including means for moving said piston assembly in a second direction opposite to the first direction, an element reciprocable in said piston assembly and sealing one end of said piston assembly to form a chamber between the element and the piston, a relief orifice for venting the chamber in the piston assembly, and a dual valve cooperating with said orifice comprising a first valve to seal said orifice and a second valve cooperating with said first valve to divide the chamher into two pressure cavities; the movement of the piston in the second direction decreasing the volume of said chamber to increase the pressure in one of said cavities to hold the first valve closed to seal said orifice, the second valve opening to equalize the pressure in both said cavities, the second valve closing when the pressure in both cavities equalizes; the increased pressure in the chamber due to the movement of the piston moving said piston assembly in the second direction against the bias of the spring additional increments of the distance the piston is moved; the biased spring tending to return the piston assembly to its initial position thereby tending to increase the pressure behind said piston for moving said piston in said second direction increasing the pressure in the other of said cavities to open said first valve, the release of pressure through said orifice premitting the biased spring to move the piston assembly in the first direction, the return of said piston assembly increasing the fluid pressure behind said piston to move said piston an additional distance in the first direction.

7. A bufier mechanism comprising, a housing containing a fluid, a hollow piston assembly reciprocable in said housing, means including a spring biasing said piston assembly in a first direction, normally closed valve means for the piston assembly adapted to be opened upon movement of said piston assembly in a second direction opposite to said first direction, a piston reciprocable 1n said hollow piston assembly including means for moving said piston assembly in said second direction, an element rcciprocable in said piston assembly and sealing one end of said piston assembly to form a chamber between the element and the piston, a relief orifice for venting the chamber in the piston assembly, a dual valve cooperating with said orifice comprising a first valve to seal said orifice and a second valve cooperating with said first valve to divide the chamber into two pressure cavities; the movement of the piston in the second direction decreasing the volume of said chamber to increase the pressure in one of said cavities to hold the first valve closed to seal said orifice, the second valve opening to equalize the pressure in both said cavities, the second valve closing when the pressure in both cavities equalizes; the increased pressure in the chamber due to the movement of the piston moving said piston assembly in the second direction against the bias of the spring additional increments of the distance the piston is moved, the biased spring tending to move the piston assembly in the first direction closing said valve means and tending to increase the pressure behind said piston for moving said piston in said second direction thereby increasing the pressure in the piston in said second direction thereby me n other of said cavities to open said first valve, the opening of the first valve of the dual valve relieving the increased pressure through the orifice to the housing; the release of pressure permitting the piston assembly to be moved in the first direction by the increased bias of the spring; said piston assembly valve means closing upon movement of the piston assembly in the first direction to increase the fluid pressure behind said piston to move said piston an additional distance in the second direction.

8. A buffer mechanism comprising, a housing containing a fluid, a hollow piston assembly reciprocable in said housing, means including a spring biasing said piston assembly in a first direction, normally closed valve means for the piston assembly adapted to be opened upon movement of said piston assembly in a second direction opposite to said first direction, a piston reciprocable in said hollow piston assembly including means for moving said piston assembly in said second direction, an element reciprocable in said piston assembly and sealing one end of said piston assembly to form a chamber between the element and the piston, a relief orifice for venting the chamber in the piston assembly, a dual valve cooperating with said orifice comprising a first valve to seal said orifice and a second valve cooperating with said first valve to divide the chamber into two pressure cavities; the movement of the piston in the second direction decreasing the volume of said chamber to increase the pressure in one of said cavities to hold the first valve closed, to seal said orifice, the second valve opening to equalize the pressure in' both said cavities, the second valve closing when the pressure in both cavities equalizes; the increased pressure in the chamber due to the movement of the piston moving said piston assembly in the second di rection against the bias of the spring additional increments of the distance the piston is moved, the biased spring tending to move the piston assembly in the first direction closing said valve means and tending to increase the pressure behind said piston for moving'said increasing the pressure in the other of said cavities to open said first valve, the opening of the first valve of the dual valve relieving the increased pressure through the orifice to the housing; the release of pressure permitting the piston assembly to be moved in the first direction by the increased bias of the spring; said piston assembly valve means closing upon movement of the piston assembly in the first direction to increase the fluid pressure behind said piston to move said piston an additional distance in the second direction, said piston assembly valve means being provided with a leak orifice to permit a retarded movement of said piston assembly in the first direction under the influence of the biased spring.

9. A buffer mechanism comprising a cylinder containing a fluid, two telescoping members in said cylinder, at least one of said members comprising a cylindrical piston assembly reciprocable in said cylinder; means including a spring tending to bias the telescoping members apart, a piston reciprocable in the piston assembly, means including said piston for telescoping said members, a cavity within said telescoping members, a relief orifice interconnecting said cavity with said cylinder, and relief valves on said piston assembly controlled by the movements of the piston including a first relief valve for sealing said orifice and a second relief valve to seal off a portion of said cavity, the movement of said piston in a given direction increasing the pressure in front of said piston within said cavity, the first of said relief valves being closed to seal said orifice while the second relief valve opens to interconnect the portions of said cavity, the increased pressure within the cavity moving the piston assembly in the given direction additional increments of the distance the piston is moved to telescope said members, the telescoping of said members increasing the bias of said spring, the second relief valve closing when the pressures in the cavity portions are equalized, the bias of said spring tending to return the piston assembly to its normal position, valve means for said piston assembly and controlled by the movement of the piston assembly, said valve means closing upon return movement of the piston assembly tending to increase the fluid pressure behind said piston for moving said piston in the given direction to increase the pressure in front of said piston, the first of said relief valves opening to relieve the pressure within said cavity through said orifice to said cylinder, the release of pressure permitting the biased spring to return the piston assembly, the return movement of the piston assembly increasing the pressure behind said piston to move said piston an additional increment of the distance the piston was moved in the given direction.

10. A butter mechanism comprising a cylinder containing a fluid, two telescoping members in said cylinder, at least one of said members comprising a cylindrical piston assembly reciprocable in said cylinder; means including a spring tending to bias the telescoping members apart, a piston reciprocable in the piston assembly, means including said piston for telescoping said members, a cavity within said telescoping members, a relief orifice interconnecting said cavity with said cylinder, and relief valves on said piston assembly controlled by the movements of the piston including a first relief valve for sealing said orifice and a second relief valve to seal off a portion of said cavity, the movement of said piston in a given direction increasing the pressure in front of said piston within said cavity, the first of said relief valves being closed to seal said orifice while thesecond relief valve opens to interconnect the portions of said cavity, the increased pressure within the cavity moving the piston assembly in the given direction additional increments of the distance the piston is moved to telescope said members, the telescoping of said members increasing the bias of said spring, the second relief valve closing when the pressures in the cavity portions are equalized, the bias of said spring tending to return the piston assembly to its normal position, valve means on said piston assembly and controlled by the movenient of the piston assembly, said valve means closing upon return movement of the piston assembly tending to increase the fluid pressure behind said piston for moving said piston in the given direction to increase the pressure in front of said piston, the first of said relief valves opening to relieve the pressure within said cavity through said orifice to said cylinder, the release of pressure permitting the biased spring to return the piston assembly, the return movement of the piston assembly increasing the pressure behind said piston to move said piston an additional increment of the distance the piston was moved in the given direction, said valve means controlled by the movement of the piston assembly being provided with a leak orifice to permit retarded return movement of the piston assembly by the biased spring.

11. A buffer mechanism comprising a cylinder constaining a fluid, two telescoping members in said cylinder,

at least one of said members comprising a cylindrical piston assembly reciprocable in said cylinder; means including a spring biasing the piston assembly in a first direction tending to move said telescoping members apart, a piston reciprocable in the piston assembly, means including said piston for telescoping said members, a cavity Within said telescoping members in front of said piston, a relief orifice interconnecting said cavity with said cylinder, a cavity in said piston assembly in back of said piston, and relief valves on said piston assembly controlled by the movements of the piston including a first relief valve for sealing said orifice and a second relief valve to seal off a portion of the cavity in said telescoping members, the movement of said piston in a second direction opposite to the first direction increasing the pressure the pressure in front of said piston,

in the cavity in front of said piston, the ,first of said relief valves being closed to seal off the orifice, the second relief valve opening due to the increased pressure in the cavity of the telescoping members to equalize the pressure in the two cavity portions, the increased pressure within the cavity of the telescoping members in front of the piston moving the piston assembly in the second direction additional increments of the distance the piston is moved to telescope said members, the telescoping of said members increasing the bias of said spring, the bias of said spring tending to return the piston assembly in the first direction, valve means for said piston assembly and controlled by the movement of the piston assembly, said valve means closing upon movement of the piston assembly in the first direction tending to increase the fluid pressure in the cavity behind said piston for moving said piston in the second direction to increase the pressure in front of saidpiston, the first of said relief valves open: ing to relieve the pressure within said cavity through said orifice to said cylinder, the release of pressure permitting the biased spring to return the piston assembly, the return movement of the piston assembly increasing the pressure behind said piston to move said piston an additional increment of the distance the piston was moved in the second direction.

12. A buffer mechanism comprising a cylinder containing a fluid, two telescoping members in said cylinder, at least one of said members comprising a cylindrical piston assembly reciprocable in said cylinder; means including a spring biasing the piston assembly in a first direction tending to move said telescoping members apart, a piston reciprocable in the piston assembly, means including said piston for telescoping said members, a cav ity within said telescoping members in front of said piston, a relief orifice interconnecting-said cavity with said cylinder, a cavity in said piston assembly in back of said piston, and relief valves on said piston assembly controlled by the movements of the piston including a first relief valve for sealing said orifice and a second relief valve to seal off a portion of the cavity in said telescoping members, the movement of said piston in a second direction opposite to the first direction increasing the pressure in the cavity in front of said piston, the first of said relief valves being closed to seal off the orifice, the second relief valve opening due tothe increasedpressure in the cavity of the telescoping members to equalize the pressure in the two cavity portions, the increased pressure within the cavity of the telescoping members in front of the piston moving the piston assembly in the second direction additional increments of the distance the piston is moved to telescope said members, the te1escoping of saidmembers increasing the bias of said spring, the bias of said spring tending'toreturn the piston assembly in the first direction, valve means for said piston assembly and controlled by the movement of thepisto-n assembly, said valve means closing upon movement of the piston assembly in the first direction tending to increase the fiuid pressure in the cavity behind said piston for moving said piston in the second direction to increase the first of said relief valves opening to .relieve the pressure within said cavity through said orifice to said cylinder, the release of pressure permitting the biased spring to return the piston assembly, the return movement of the piston assembly increasing the pressure in the cavity behind said piston to move said piston an additional increment of the distance the piston was moved in the second direction, said valve means being provided With a leak orifice to permit retarded return movement of the piston assembly by the biased spring.

13. A butter mechanism comprising, a housing containing a fiuid, two telescoping piston members within said housing, at least one of said members comprising a hollow piston assembly reciprocable in said housing; means for biasing said telescoping members apart, valve means for said piston assembly, said relief valve being closed by the extension of the telescoped members, a reciprocable piston rod extending into both of said telescoping members and bounding a space within said members, a piston secured to said rod and engageable with one end of the hollow piston assembly, an orifice venting the space bounded by the piston rod within the telescoping members to said housing, and dual valve means for sealing said orifice, said dual valve means including means normally dividing said space into a first cavity and a second cavity, the movement of said piston rod in a direction to move said hollow piston assembly and telescope said piston members against the bias of said biasing means increasing the fiuid pressure within the second cavity to open said dividing means to equalize the pressures in both cavities, the increased pressure Within the cavities moving said piston assembly additional increments of the distance the piston is moved and in the same direction, the fluid pressures in the first and second cavities equalizing and said dividing means closing when movement of said piston rod ceases, said biasing means tending to extend said telescoped members and thereby tending to increase the fiuid pressure within said piston assembly behind said piston for moving said piston to increase the pressure in said first cavity, said dual valve means opening upon increase in the pressure in'the first cavity, the release of pressure through said orifice permitting the biasing means to extend the telescoping members to increase the pressure behind said piston to move said piston and rod an additional increment of the distance the rod was moved.

References Cited in the file of this patent UNITED STATES PATENTS 

